For years, the Port Authority bus terminal in midtown Manhattan has seemed frozen in time, a forgotten giant in the agency’s vast portfolio of transportation facilities. As recently as a few months ago, the agency said it had no plans for major changes to the cramped and outdated building over the next decade.

But that changed dramatically on Wednesday, with the agency’s commissioners suddenly agreeing not only to start $90 million in repairs this year but also vowing to move aggressively to replace the world’s busiest bus depot, which several officials described as “unacceptable.”

The sudden change of course — along with the commissioners’ newly-adopted urgency — seemed to take even the agency’s harshest critics by surprise. But it came as the Port Authority desperately tries to move on from the George Washington Bridge lane closure scandal by proving it can adequately respond to the region’s most basic transportation needs.

The seeds were sown earlier this summer with a campaign led by a vocal New York-appointed commissioner and a New Jersey state senator. And that campaign found a receptive figure in a new chairman who took the reins of the scandal-plagued agency on Wednesday and quickly seized on a very visible and high-impact cause.

“The clear consensus is that a new bus terminal will be necessary,” John J. Degnan, who was elected chairman at Wednesday’s meeting, said before $90 million was approved for repairs that are expected to begin in September. Degnan took a tour of the building on Monday with New York’s ranking commissioner, Scott Rechler. Rechler, a three-year commissioner and the board’s vice-chairman, said Wednesday that the tour “illuminated the fact that this terminal is in bad shape.”

“It is obsolete in every way you can imagine,” he added.

Earlier this year commissioners voted to approve a 10-year spending plan that would have spent $170 million to maintain the terminal over the next decade but contained no major improvements. Rechler said Wednesday that he was “concerned” that none of the commissioners had raised the bus terminal as a top priority during the years they spent developing the plan through an exhaustive process.

“I was a little dismayed that we spent two years going through this capital plan and getting input from all the commissioners who were taking feedback from the community and it didn’t reach that level, and I’m not exactly sure why,” he said.

In contrast, on Wednesday the board moved so quickly that agency officials said they had not developed all of the details of the $90 million bus terminal improvement plan.

But they said it would include new air conditioning units, improved cellular telephone reception, revamped bathrooms on the second floor, and fixes for ceiling leaks. Those details will be laid out in September, they said, and the improvements will begin around the same time. They also said they were exploring new strategies to improve the flow of buses into the terminal, as well as street-level bus gates.

Degnan, who proposed the $90 million authorization Wednesday, called the current condition “insulting” to commuters.

“It undermines the public’s credibility in an agency like this,” he said.

Degnan replaces former chairman David Samson, who resigned amid the lane closure controversy and questions about whether the clients of his law firm benefitted from Port Authority decisions. Degnan has said ethics and transparency are his top priorities and that he wants to restore the agency’s public standing.

On Wednesday, agency officials also said they would begin discussing how to finance — and where to build — a new bus terminal as early as this fall. An outside firm has been working on a study to provide options for long-term improvements. Officials said Wednesday they would instruct the authors of the study, expected to be completed early next year, that a new terminal was the No. 1 option.

But there are considerable hurdles before commuters will reap the benefits of a new bus terminal.

Most significantly, was the question of how the agency would pay for a project that is expected to cost at least $1 billion, if not more. Officials said they would discuss in the future months what projects the bus terminal might replace in the $28 billion, 10-year capital plan. Others questions include where in Manhattan a new terminal would be located and, if it were to be rebuilt at the same 8th Avenue and 42 Street location, where bus traffic would head during construction.

As for timing, Degnan said during the meeting that a new terminal was probably 10 to 15 years away, but he later backed off that estimate as speculative.

More than 200,000 people use the bus terminal each day, significantly more than when it opened in 1950. That figure already matches the combined total who use NJ Transit rail lines and the PATH train to cross the Hudson River each day, and it is projected to grow rapidly over the next decade, agency officials said.

Getting buses in and out of the terminal is a major problem, especially during the evening commute, when they return to Manhattan empty from New Jersey because there is not enough room for parking east of the Hudson. The buses have gotten bigger since the building was designed, and have more difficulty maneuvering through the four-level terminal. The congestion caused by buses waiting to get inside the terminal can extend well beyond the New Jersey side of the Lincoln Tunnel.

But significant improvements have been deferred over the years, amid on-again and off-again negotiations with private developers interested in building above the terminal.

Major upgrades to the terminal were envisioned as a part of any deal, but advanced talks on development deals ended in 2012, and the Port Authority was left with a neglected bus terminal that also loses about $100 million a year in operating costs.

Then came the lane closure scandal, a disagreement over funding a private office tower at the World Trade Center site, and a persistent and vocal New York commissioner, Kenneth Lipper.

Lipper, a critic of a plan to back private construction loans for World Trade Center developer Larry Silverstein, said earlier this year that the agency should instead direct the money to the bus terminal. At the time, Lipper had already voted to approve the 10-year capital plan without a bus terminal replacement project.

And this summer, state Sen. Loretta Weinberg, a Teaneck Democrat, began attending Port Authority meeting regularly, fiercely advocating for improvements at the terminal after hearing complaints from her constituents and criticizing commissioners for neglecting the facility.